The present application is directed to bone pins and wires, and, more specifically, to bone pins and wires used to attach a bone fragment to an anchor bone for a healing duration. Further, the present application is directed to bone screws which are used to attach a bone fragment to an anchor bone for a healing duration, and to a method of using such bone pins, wires and screws, which may involve manipulating the bone fragment relative to the anchor bone during the fixation surgery.
Bone pins and wires are characterized by having a relative small diameter, such as a diameter of 0.1 inches (2.5 mm) or less. Bone pins which are elongated wires are commonly referred to as “Kirschner wires” or “K-wires”. An example of this is disclosed in U.S. Pat. No. 2,393,694 to Kirschner. The term “bone pin” is more commonly used for shorter structures, such as a length of 2 inches or less, while the term “K-wire” more commonly applies to longer structures, such as a length up to 12 inches, but there is no bright line definition clearly distinguishing between a “bone pin” and a “K-wire” based on length. The present application uses the term “bone wire” to refer to such a small diameter structure and including either a bone pin or a K-wire, regardless of length, but excluding, for instance, a larger diameter bone screw. The present application uses the term “bone screw” to refer to threaded bone fixation devices having a diameter greater than 0.1 inches (2.5 mm).
Bone wires have long been used in the orthopaedic arts for several different purposes. Bone wires are often used during surgery as a temporary guide in targeting and directing another more permanent device, such as a cannulated bone screw running over the bone wire, into a bone fragment or anchor bone. Bone wires have been implanted to anchor other devices, such as a bone plate, fixator or external splint device, to a fractured bone. Bone wires have also been used to secure many types of bone fragments to anchor bones, where the term bone “fragment” refers to any part of bone separated by a fracture, regardless of whether that fracture is partial or completely through the bone.
Bone wires commonly have a pointed tip, which may be further fabricated with a drill type structure such that rotation of the bone wire about its longitudinal axis helps to remove bone material from the hole into which the bone wire is advanced. The bone wires may or may not have fine threads to further assist in axially advancing the bone wire into its hole during rotation. While bone wires have been used for fragment fixation, design improvements are needed to have a small diameter bone wire structure which more easily places an appropriate compression force on the interface between the bone fragment and its anchor bone.
Bone screws have also long been used in the orthopaedic arts. Bone screws are typically used for permanent or semi-permanent fixation, either attaching a larger bone fragment to an anchor bone, or attaching a stress-supporting fixation device, such as a bone plate or intramedullary nail, to an anchor bone. Many different constructions of bone screw are known. The bone screws can have specific thread designs, including self-tapping threads distally for insertion and self-tapping threads proximally for extraction. The bone screws can have heads of specific designs, such as to induce rotation or pivoting of the bone screw upon advancement or retraction. Bone screws are typically fabricated at a diameter to support the torque with which the bone screw will be advanced as well as the shear forces to which the bone screw will likely be subjected. Bone screws are typically selected at a length dependent upon the location and orientation of use, such that the entire bone screw during use will reside within the profile of the patient's tissue.